The invention relates to an electrical press-in contact element with at least one press-in section, which extends in a direction of extension from a root area, in which the press-in section is connected with a contact body, up to a free end, and which has a middle zone flanked on either side by a respective edge zone from the root area up to the free end, wherein the edge zones form contact surfaces facing away from each other that, once the press-in section has been inserted into a press-in opening, for example of a circuit board, abut against the wall of the press-in opening.
A press-in contact element is previously known from DE 198 31 672 B4. The press-in contact element disclosed therein has a press-in section, which is connected with a contact body. The contact body has a contact element. The press-in section is pin-shaped, and can be made to abut in a conductively connecting, resiliently biased manner against the inner wall of a hole in a circuit board that forms a press-in opening. The force for pushing the press-in section into the through connected hole of the circuit board is applied by impinging upon a push-in shoulder formed by the contact body. The bulbous or inclined shape of the contact used in prior art has here proven advantageous for achieving the lowest possible press-in forces up until reaching its largest envelope circle diameter. Such press-in contacts are used for manufacturing solderless connections according to DIN EN 60352-5, and designed in the longitudinal direction starting from the press-in end with an integrally connected plug end, connection area or pressed screen.
In order not to damage the circuit board and its through-hole plating, and in particular its inner conductor paths, in the pressing in process, it makes sense that the press-in section be resilient in design, and press against the hole wall with a relatively slight force. To achieve this, the goal is to have a relatively slight normal force for the legs of the press-in sections abutting against the hole wall. However, the force required to push the press-in sections out of the circuit board perforations must be relatively high for reasons of stability, in particular given freestanding contacts. Important in terms of quality, this requirement cannot be satisfied given slight material thicknesses for the press-in contact formed by the press-in sections, however, in particular if the normal force of the legs of the press-in contacts is low. A slight push-out force or even retention force is also disadvantageous during vibration loads that arise in automotive applications in the engine compartment, since the contacts can become loosened, which increases the contact resistance. This type of damage can result in the complete failure of the electrical connection.
Such press-in contacts are often integrally connected with continuing areas. The latter can be designed as socket contacts for round or flat plugs, crimped connections, insulation-displacement connections, foil connections or pressed screens, etc. Such applications require elastic, resilient properties to enable a flawless contacting with the mating plug or connecting piece. For this reason, the material thickness is often slight, for example 0.3 mm. However, this thickness is occasionally insufficient for satisfying the above requirements placed on such press-in contacts. In particular, the slight material cross sections and relatively small contact surface in the circuit board perforation often make it impossible to achieve the desired high current carrying capacity as well as the desired cold welding. For this reason, such components are manufactured out of step-milled strip material in prior art. This means that the strip with an exemplary thickness of 0.8 mm for the press-in zone area must be reduced to 0.3 mm in the area of the adjoining contact regions. Since this process usually takes place via milling, such strips are expensive. Press-in contacts like these fabricated out of a blank strip are usually provided with a galvanic surface in an additional step. The latter consists of pure tin due to the required cold welding with the through-hole plating of the circuit board and the unleaded regulation. However, surfaces galvanically plated with pure tin are known to be susceptible to whisker formation when exposed to the pressure and bending load that arises in a press-in connection. These whiskers are undesirable, and can cause short circuits during application. In addition, the continuing areas are often made out of pre-coated strip for costs reasons, and thus have blank cutting edges. The latter can be disadvantageous when used as a contact surface in press-in contacts in the through-hole plating of the circuit board. Therefore, these press-in areas are galvanically coated in a separate operation in prior art. This additional operation is very cost-intensive and complicated.
Prior art further includes DE 38 31 508 C2 and U.S. Pat. No. 4,017,143, which each show an electric press-in contact element, in which a cross sectional profile is imparted to the press-in section via embossing with a die stamp.
U.S. Pat. No. 6,132,225 discloses a press-in section that is curved over its entire direction of extension around a single bending line, thereby forming edge zones that project from the original extension plane of the sheet metal blank.
DE 10 2014 107 438 A1 discloses a slotted press-in section with an impressed recess.
DE 20 2009 009 933 U1 discloses a slotted press-in section with bilateral impressions, so that webs form in a contact area.
DE 20 2016 102 148 U1 discloses a press-in section consisting of two parallel legs.
EP 0 313 300 A1 discloses a press-in section, wherein a groove with a V-shaped cross section is impressed into its contact area.
DE 90 16 257 U1 and DE 10 2015 200 491 A1 disclosed press-in sections with troughs impressed into the contact area.
DE 11 2006 000 095 T5 discloses a press-in section with legs that are separated by a free space and can be resiliently moved toward each other.